Two Japanese navy helicopters carrying eight crewmembers were believed to have crashed in the Pacific Ocean south of Tokyo during a night-time training exercise, and rescuers were searching for the missing, Japan’s defense minister said, Ednews informs via NBC News.

The two SH-60K choppers belonging to the Maritime Self Defense Force and carrying four crew each, lost contact late Saturday near Torishima island in the Pacific, about 370 miles south of Tokyo, Defense Minister Minoru Kihara told reporters.

One of the eight crewmembers was recovered from the waters, but his or her condition was unknown. Officials were still searching for the other seven.

The cause of the crash was not immediately known, Kihara said, adding that officials are prioritizing the rescue operation.

The MSDF deployed eight warships and five aircraft for the search and rescue of the missing crew. They recovered fragments believed to be from one of the SH-60Ks, Kihara said.

“We believe the helicopters have crashed,” he said.

The helicopters, twin-engine, multi-mission aircraft designed by Sikorsky and known as Seahawk, were on night-time anti-submarine training in the waters, Kihara said. One lost contact at 10:38 p.m. after sending an emergency signal. The other aircraft lost contact about 25 minutes later. One belonged to an air base in Nagasaki, and the other at a base in Tokushima prefecture.

The SH-60K aircraft is usually deployed on destroyers for anti-submarine missions.

Saturday’s training only involved the Japanese navy and was not part of a multinational exercise, defense officials said. They said no foreign aircraft or warships were spotted in the area.

Japan, under its 2022 security strategy, has been accelerating its military buildup and fortifying deterrence in the southwestern Japanese islands in the Pacific and East China Sea to counter threats from China’s increasingly assertive military activities. Japan in recent years has extensively conducted its own naval exercises as well as joint drills with its ally the United States and other partners.

Saturday’s apparent crash comes a year after a Ground Self-Defense Force UH-60 Blackhawk crashed off the southwestern Japanese island of Miyako, leaving all 10 crewmembers dead. In January 2022, a Air Self-Defense F-15 fighter jet crashed off the northcentral coast of Japan, killing two crew.

Japan’s NHK public television said no weather advisories were issued in the area at the time of Saturday’s crash.